The present invention relates to an apparatus for delivering fuel from a fuel tank to an engine in a motorized vehicle. More particularly, it relates to an apparatus for delivering fuel from a fuel tank to an engine in a motorized vehicle in such a manner that the fuel drawn from the vehicle's fuel tank approximates the average fuel composition of the fuel in the main fuel tank, even if the fuel is stratified.
It is well known that ever tighter emissions regulations and petroleum depletion have prompted research into the feasibility of using alternative fuels in motorized vehicle engines. Currently, ethanol/gasoline and methanol/gasoline mixtures are among the alternative fuel possibilities being considered.
Alternative fuel mixtures exhibit physical properties and performance characteristics which are different from pure gasoline, including dissimilar combustion burn rates, volumetric energy content, vapor pressures, octane ratings, and heats of vaporization. The operating parameters of vehicle engines utilizing alternative fuels must be adjusted to accommodate such differences in order for the engines to operate efficiently. The operating parameters which must be adjusted include the air bypass, fuel flow, spark timing, and air/fuel ratio.
The aforementioned adjustments can be made automatically by an engine control computer. Engine control computers are well known and are commonly used in vehicles. See, for example, U.S. Pat. No. 4,706,630 to Wineland et al. However, in order for an engine control computer to correctly make the requisite adjustments, the instantaneous composition of the fuel being burned in the engine must be known by the computer. To the extent that fuel composition information sent to the engine control computer differs from the actual composition of fuel being burned in the engine, adjustments made to the engine will be improper. Improper engine adjustments, in turn, can result in poor engine performance and excess emissions due to incomplete combustion. Thus, a close correlation between the composition of fuel actually being burned in an engine and that which is made known to the engine control computer is needed to facilitate the use of alternative fuel use in motorized vehicle engines.
Current means of drawing fuel from the fuel tank of a motorized vehicle involve devices which either draw fuel from the top layer of fuel in the fuel tank or from the bottom of the fuel tank. For example, U.S. Pat. No. 1,203,578 to Brooks discloses a delivery pipe attached at one end to a float and strainer combination for drawing fuel from the upper portion of fuel within a fuel tank. The float keeps the strainer at the top surface of fuel in the tank so that only fuel from the top surface is drawn through the strainer.
U.S. Pat. No. 3,390,698 to Carmichael et al. discloses a vehicle with an auxiliary fuel tank which receives fuel from the bottom of a main fuel tank. The auxiliary tank is provided with an outlet fuel line having small bores to restrict fuel flow to the vehicle's engine when the only fuel remaining in the vehicle is that contained within the auxiliary tank. As the fuel level in the auxiliary tank drops, the number of orifices available for fuel delivery to the engine become fewer and fewer so that the top speed of the vehicle becomes progressively lessened. In addition, the bores which are exposed above the fuel level in the auxiliary tank allow air to be ingested into the vehicle's engine which causes the engine to sputter. In this manner, the driver is reminded to refuel the vehicle.
U.S. Pat. No. 4,546,750 to Brunell et al. discloses a vehicle fuel tank which has a filter at the bottom thereof and a secondary reservoir disposed above the filter. Fuel is drawn from the interior of the filter. The secondary reservoir is filled by a fuel return line from the vehicle engine. An inertia responsive valve is provided between the reservoir and the filter to allow fuel to pass from the reservoir to the filter when the vehicle undergoes acceleration. In this manner, fuel starvation is prevented during acceleration.
Because such traditional fuel drawing devices draw fuel exclusively from the top layer of fuel in a fuel tank or from the bottom layer, only that layer of fuel from which the pickup device is drawing will be sent to the engine. In the event that the fuel consists entirely of one component, the portion of fuel sent to the engine will be representative of the fuel in the tank. In this instance, existing fuel drawing devices would be adequate. However, in other situations where the fuel either consists of multiple components, such as combinations of gasoline, methanol and ethanol, contains various fuel additives, or contains water, the composition of each layer of fuel in the fuel tank may differ. The condition in which the composition of each layer differs, known as stratification, generally occurs when the vehicle has been stationary for a period of time or after the vehicle has been refueled with a fuel having a different composition than the fuel initially in the tank. In this regard, the lower the temperature or the higher the water content in the fuel, the greater will be the likelihood that a condition of stratification will occur. During a condition of stratification, a fuel drawing device of the prior art will draw fuel from only one layer, thereby sending a portion of fuel to the engine which differs from the average fuel composition in the fuel tank.
For example, with a stratified fuel consisting of 85% methanol and 15% gasoline in a fuel tank, the higher density methanol will tend to settle towards the bottom of the tank while the gasoline will collect at the upper portion of the fuel in the tank. During the period of stratification, a surface-drawing fuel pickup device will send fuel consisting mostly of gasoline to the engine, while a bottom-drawing device will send a largely methanol-laden fuel. This situation can be problematic in several respects.
As is well known, in-line fuel sensors are commonly used to convey to a vehicle engine control computer the composition of fuel being sent to the vehicle's engine. Agitation of the fuel by vehicle motion or by action of the fuel pump will cause the composition of each layer of fuel to change over a period of time until the fuel is fully mixed. In addition, with a bottom drawing fuel pickup, fuel consumption will cause the composition of the bottom layer of fuel in the fuel tank to continuously change until full mixing occurs. Both of these events will result in continuously differing compositions of fuel being sent to the vehicle's engine. Due to the distance between the fuel sensor and the engine, the fuel composition information being sent to the engine control computer will differ from the composition of fuel actually being introduced into the engine. The result will be improper engine adjustments being made by the engine control computer during the period between stratification and full mixing.
A similar problem can occur due to the fact that, at startup, the composition of fuel in the fuel injector header and in the fuel lines between the fuel pump and the header will be different from the composition of fuel at the particular layer of fuel from which a surface or bottom drawing fuel pickup system will take fuel. Again, the composition of fuel being introduced into the engine will continuously vary and the distance between the fuel sensor and the engine may result in erroneous adjustments being made to the engine by the engine control computer.
As an alternative to using a fuel sensor, a vehicle engine control computer can be informed of the composition of fuel in a vehicle by providing means to manually specify to the vehicle's engine control computer the composition of fuel being added during each refueling. The engine control computer can be programmed to use this information, along with the total quantity of fuel added to the fuel tank and the composition and quantity of fuel existing in the fuel tank prior to refueling, if any, to calculate the average fuel composition in the fuel tank following refueling. Such means are disclosed in my commonly-assigned U.S. application Ser. No. 07/832,459, filed Feb. 7, 1992, entitled "Fuel Specifying Apparatus," the disclosure of which is hereby incorporated by reference. As with the use of fuel sensors, stratification of the fuel could result in erroneous engine adjustments being made by the vehicle engine control computer with the system disclosed in application Ser. No. 07/832,459 inasmuch as the composition of the layer of fuel being instantaneously drawn by a surface or bottom drawing fuel pickup device may differ from the average fuel composition in the vehicle fuel tank. Since the engine control computer will have adjusted the vehicle engine parameters based upon the average composition of the fuel in the fuel tank, the fuel actually being introduced into the engine may be inefficiently combusted due to the fact that the engine adjustments could be improper for that fuel.
Accordingly, it is seen that a need exists in the art for a system for delivering fuel from a vehicle fuel tank in such a manner that the fuel being withdrawn approximates the average composition of the fuel in the tank. Such a need, if fulfilled, would facilitate the use of multicomponent, alternative fuels in motorized vehicles by allowing engines to operate efficiently on such fuels, resulting in maximum engine performance and minimum pollution.